Intravascular ultrasound imaging systems (IVUS) are used to obtain ultrasound images inside a patient's body. An IVUS system typically includes an ultrasound catheter having a flexible catheter body adapted for insertion into the vascular system of the patient. To obtain ultrasound images, the catheter comprises an imaging core received within a lumen of the catheter body. The imaging core comprises an ultrasound transducer connected to the distal end of a flexible drive cable that extends to the proximal end of the catheter through the catheter lumen. The drive cable is used to rotate and longitudinally translate the transducer within the catheter lumen. The catheter includes electrical and mechanical connectors for electrically and mechanically connecting the catheter to a motor drive unit (MDU). The MDU includes a motor for rotating the imaging core, and transmits electrical signals to and from the transducer.
Currently two types of connections are used to connect the catheter to the MDU. The first type uses a stationary connector in which the rotating wiring of the transducer is converted to stationary wiring by means of a rotary transformer, slip ring or capacitive device housed in a catheter hub. Disadvantages of this approach include increased cost, increased hub size, and increased complexity. Because a rotary transformer or slip ring is installed in each catheter, there is the additional cost of purchasing or manufacturing the transformer or slip ring for each catheter as well as the additional labor cost for assembly. Also, the rotary transformer must be accommodated in the catheter hub, and as other signals are added, the size of the transformer, and hence the hub, may have to be enlarged. A catheter with a rotary transformer is more complex and requires that the fit of the components be within close-tolerances to perform this type of catheter cannot be tested until final assembly, at which time, if there is a problem with the catheter, the entire unit must be strapped.
The second type of connection uses a coaxial-type connector in which the mating contacts comprise a center pin and concentric spring loaded rings so that the catheter and MDU are properly mate regardless of the relative position of their connectors. The rotary transformer or slip ring that converts the rotating wiring to stationary wiring is house in the MDU. Disadvantages of this approach include limitations in the number of contacts available, greater complexity, and the potential for slippage in the mechanical coupling. The cost of the multiple contact coaxial connector can approach that of the rotary transformer. For more than two contacts, the coaxial connector becomes larger, complex, and expensive. Typically the contacts of the coaxial connector act as a mechanical coupling to transmit torque from the motor drive to the rotating portion of the catheter, and as the contacts in the motor drive wear, slippage can occur.
Therefore, there is a need for improved rotational connectors that overcome disadvantages of the prior art.